The use of a hand operated pointing device for use with a computer and its display has become almost universal. By far the most popular of the various devices is the conventional (mechanical) mouse. More recently, portable computers have become available which incorporate pen based input devices. These computers use an electronic pen to write data on a display or to select data presented on the display. To use a pen based computer, the computer user holds the electronic pen and writes on the surface of the associated display. The electronics in the pen and computer compute the position of the pen relative to the display and perform the function requested by the user of the computer. The display on a pen based computer needs to be flat to enable the user to write on the display surface conveniently and requires a special type of display that can detect the position of the pen touching the surface of the display. Other types of pen and pen-like pointing devices, such a stylus, suffer a similar limitation: They must be used on a special surface such as a graphics tablet.
Limiting the use of a pen based pointing device to a special surface limits the usefulness of such a device. When the special surface is a display screen, that screen inconveniently needs to be laid flat to write in a conventional manner. When the special surface is a graphics tablet or similar device, that tablet needs to be hauled around with the computer. Furthermore, both of these devices limit to a small region the area upon which writing or pointing may be done and still be captured by the computer.
Accordingly, there is a need in the art for a reliable and intuitive way to perform pointing function for a desktop or a laptop computer that functions on almost any surface. It is desirable that this pointing device be capable of inputting freehand text and drawings in a pen-like manner without additional hardware. Finally, it is desirable that this device not have any cables or wires that may get tangled or otherwise interfere with the writing process connecting it to the computer.